There was a show I used to watch that aired in either the early or mid 90's on (I think) PBS. It was with live actors, and was about a man who owned a restaurant and was also a scientist who built a time machine in the back. A group of kids and him would use it to travel back in time, and he was always worried about the machine being discovered. I think in one episode (maybe the last) his assistant voluntarily stays behind in the middle ages. Appreciate any help!